It is well known that flexible poly bags are widely used in the packaging industry. It is further known to provide such bags on a continuous roll with individual bags being connected at a perforation. Accordingly, various machines and methods have been developed to rapidly open, fill, and seal such bags. Typically, bags are threaded through a series of rollers which are mechanically driven by an electric motor. The bags are passed beneath a continuous and/or pulsed air stream which serves to open the bag, at which time the bag may be filled either manually or automatically. The bag may then be sealed using either an adhesive or a heat sealing technique. Such heat sealing techniques typically involve the use of a heated seal bar which is briefly held in contact with the bag by a clamping mechanism. The heated seal bar is usually coated or covered with a non-stick material which is often provided in the form of a woven fabric. While these types of materials are highly effective in preventing the bag material from sticking to the seal bar, the extreme heat and frictional forces require that the material be frequently rotated or replaced.
Another disadvantage with known systems is that the mechanism for clamping the bag against the seal bar is subject to interference of objects which are accidentally interposed between the clamping mechanism and the seal bar. Such obstructions tend to damage the machine or otherwise jam the bag path. Accordingly, it has been known to provide interference sensors, in the form of optoelectronic devices which are often quite expensive.
It is further known to provide such machines with means for separating individual bags from one another at the perforation after sealing. Known systems for accomplishing this function have generally involved the use of a brake on the main drive roll to maintain the trailing edge of the bags in a fixed position while the bag to be detached remains clamped between the seal bar and the clamp mechanism. The clamp and seal mechanism is then moved away from the drive rolls, thereby causing the bag to separate from the roll at the perforation. This is typically accomplished by pivoting the clamp and seal bar mechanism relative to the rolls. The rather severe movement required produces a great deal of vibration and requires heavy duty hardware, increased maintenance and adjustment measures, and multiple actuation mechanisms. More recently it has been known to separate perforated bags by disengaging the drive roll from the drive motor, braking the roll, and then temporarily reversing the drive roll by way of a servo-drive or stepper motor while the bag to be sealed remains clamped at the seal bar.
Known sealing mechanisms employed in automated packaging devices provide a flat, spring-bias, plate with an aperture therethrough, wherein sharp serrated teethes surround the aperture. On one side of the flat plate aperture is a fixed heated seal bar. Disposed on the other side of the flat plate is a movable gripper bar. A plastic bag is received between the gripper bar and the spring-bias plate, whereupon the gripper bar engages the bag and the flat plate moves the bag into contact with the seal bar for sealing the plastic bag. After sealing, the bag is pulled in a known manner against the serrated teeth to remove the bag from its attached web. These known sealing mechanisms provide several disadvantages. One disadvantage is that the flat plate is costly to provide, especially with the serration needed to remove the bag from the web. It is known that the serrations wear and are expensive to replace. Moreover, the serrations tend to be very sharp and can be dangerous to the person using the packaging machine. Finally, the springs employed to bias the flat plate tend to wear which requires adjustment to the gripper bar to obtain the proper application of force during the sealing procedure.
Based on the foregoing, there is a need in the art for a sealing mechanism which is long lasting, safe to use and which provides a reliable seal that is here to forbid not unknown in the art.
Thus it is desired to obtain a packaging apparatus and method which will serve to overcome the foregoing disadvantages.